The present invention relates to a device, in particular a work table for projectors, for providing positioning, registration and displacement, and is useful, in particular, as a work table, for reduction projectors (for example, for electron beam lithography applications or projection mask aligners) and for measuring structural properties using scanning electron microscopes).
High-precision devices providing positioning, registration and displacement in electron beam lithography and scanning electron microscope applications require a positioning and registration accuracy in the order of 0.001 microns. A device for positioning, registration and displacement is disclosed in U.S. Pat. No. 4,575,942 and includes a four-stage design. Instead of the conventional two-dimensional device for precise positioning along the X axis and Y axis, a precision plate is employed which is held on a coarse carriage by flexible attachments and is moved by at least three linear drives. This design is quite complex.
It is thus an object of the present invention to provide an improved displacement device, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved displacement device which is simple in construction and yet is capable to provide a displacement device operating in two directions, while allowing a precise measurement of the distance and size of the area.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a two-dimensional table to provide positioning and displacement, and a registration unit for providing registration between markers, with the registration unit supported on a carriage of the table via flexible articulated supports and movable by a plurality of drives, preferably by seven drives.
According to another aspect of the invention, a bi-level device is provided which includes a first level (first stagexe2x80x94a high-precision dimensional table comprised of a device for linear displacement with flexible elements) and a second level (second stagexe2x80x94a high-precision six-stage device which enables displacement in the coordinate directions X, Y, Z, OX, OY, OZ).
The present invention realizes a high-precision device for providing positioning, registration and displacement in two directions, which, instead of the conventional two-dimensional device for precise positioning along the X and Y directions, employs an additional 6-stage device which is supported by one of the carriages of the dimensional moving table by pivot bearings, and is moved by at least seven linear drives.
According to another feature of the present invention, the two-dimensional table is designed for linear displacements in two directions and includes drives having flexible elements to provide displacement and positioning in these two directions.
Suitably, the device for registering and adjusting allows high-precision displacements and motion reversal of the dimensional table in three coordinate axes.
According to another feature of the present invention, an attachment device which preferably includes the four flexible joints to which a moveable frame and a base plate are attached, is provided on the at least one carriage of the two-dimensional table.
The drives may be implemented in form of identical linear electric drives adapted to move the dimensional table together with a plate, which is mounted on the table, with high precision in six coordinates X, Y, Z and OX, OY and OZ. Suitably, two of the seven linear drives together with a moveable lower frame and the base plate form the device which provides high-precision displacement in the X and Y directions. Three of the seven linear drives may be secured to the base plate and activate the motion of the upper moveable frame, thereby providing a device with extremely precise displacement along the Z axis and tilt about the axes OX, OY. Two of the seven drives may be secured to the upper moveable frame, representing a table with reversible movement about the OZ axis.
Preferably, the linear drives have an electric motor and a three-stage lever gear.
According to another feature of the present invention, the overall transmission ratio of a link gear mechanism is five hundred. Preferably, two displacement sensors are arranged on an input drum and an output drum of the gear mechanism. One of the sensors may be designed for controlling the drive via the electric motor, while the other sensor may be designed to measure and indicate the reversing angle of the working element of the device.
According to another feature of the present invention, the two one-dimensional devices may be provided with multi-track slideways for a plurality of balls which are separated by spacers.
The device according to the present invention may further include a frame made of an upper and a lower moveable frame section, a base plate, and a work table on which a sample to be measured is placed. The work table can be displaced with the linear electric drives in the coordinate directions X, Y, Z and rotated about the axes OX, OY and OZ.